This one really is too close to call.

It’s election day, and Bay State residents are being hammered with a final frenzy of advertising aimed at convincing them that presumed frontrunner Democrat Martha Coakley or Republican Scott Brown is an inadequate candidate for the U.S. Senate seat left vacant by the death of Sen. Edward M. Kennedy. Nothing is for sure in a race that once seemed like a lock for Coakley.

If the presence of political heavyweights like President Barack Obama, former President Bill Clinton and former New York Mayor Rudolph Giuliani stumping for Coakley and Brown were not enough to reflect the tightness of this race, polls from across the state and nation paint a picture of ambivalence from registered Democrats and widespread embitterment with politics as usual.

One thing is certain in this unexpectedly close election: Independent voters now hold in their hands the fate of whom the Commonwealth will send to Washington.

According to Andrew Smith, survey center director at the Carsey Institute at the University of New Hampshire, 51 percent of voters in Massachusetts are not registered with the Democratic or Republican party. Among independents, the race is practically a dead heat, with the Carsey Institute’s most recent poll showing support split at 47 percent for both state attorney general Coakley and state Sen. Brown.

Smith emphasized that Tuesday’s vote is particularly hard to predict, as special elections always see lower turnout than general elections and less voter participation from groups expecting victory. This gives Brown an advantage, as Democrats outnumber registered Republicans by a factor of three to one in Massachusetts. However, with a low turnout from registered voters and high participation from independents, anything is possible.

“My sense is still that Coakley wins, but that it’s going to be much closer than anticipated,” said Smith. “There are just so many more Democrats in Massachusetts than there are Republicans, and despite Republicans’ current advantage in excitement and motivation, I don’t believe that there’s enough of that anger to compensate for the absolute numbers of Democrats in this state,” he continued.

Smith stressed that this election would be difficult to track as, despite sheer numbers, further polling reveals that among people likely to actually go the polls, the race is virtually tied.

“If you look at just party registration, it’s 36 percent Democrats, 48 percent unregistered, 13 percent Republicans and three percent other,” said Smith.

“What that doesn’t reflect is who actually is going to show up on election day,” he said. “We saw that of the people most likely to vote, the people who will definitely vote on election day, it was a tie between Brown and Coakley, and among those people who said they were definitely going to vote, Coakley held a narrow lead,” Smith continued.

David Paleologos, director of Suffolk University’s Political Research Center, said that support had been gravitating toward Brown since a debate last Monday and that this momentum was generated by slip-ups by Coakley and a strong media push by the Brown campaign. Suffolk’s poll, conducted Jan. 11 to 13, had Brown leading by four points, but ahead 65 to 30 percent among independents. Independents accounted for 45 percent of the survey, Democrats representing 39 percent and Republicans representing 15 percent.

“We’ve had a scenario where it looks like Brown is opening up a lead, where previous polls had Coakley ahead,” said Paleologos of his poll.

“You’ve had a lot of forces at play,” Paleologos said of Brown’s surge in popularity, “a good debate performance by Brown, a backdrop of dissatisfaction about healthcare and the economy and all of this has been dovetailing towards Brown.”

Paleologos said he believes Brown’s recent gains could be too much for Coakley to overcome and could propel him to the Senate.

“I think [Brown’s gains] have continued through the end of the week and into the weekend, and while I think Obama’s presence could have helped in certain demographics, whether you can reverse these wholesale gains in a few days, I don’t think so,” he said.

“Statistically, I see him as more viable at this point,” Paleologos said of Brown. “He is affecting more demographics, and in areas where he’s winning, he’s winning big, and in areas where he’s losing, he’s not losing by much.”

Smith, on the other hand, predicted a tight Coakley victory, but said that turnout will be the deciding factor.

“You have to pay attention to turnout – who shows up,” he said. “Turnout is differential, it doesn’t mean that equal percentages of Republicans and Democrats show up; right now Republicans have an advantage there,” said Smith.

Smith cited voter dissatisfaction with early results from Obama administration policy as key in support drifting towards Brown as, he explained, voters blame the party in power when times are tough.

“Most voters don’t pay attention to politics,” he said. “But they do pay attention to their pocketbooks and their jobs.”

“So, fair or not fair, that puts blame on the party of the president, and so there’s a kind of general malaise towards the Democrats right now, even from Democrats,” Smith said.

He also said that while independent can be something of a relative word, these numbers indicate that people who are dissatisfied with political parties are more likely to support Brown and his limited government platform.

Brown has strongly attacked President Obama’s healthcare proposals as well as any new taxes, while Coakley has stood behind most of the Obama administration’s stances, promising to vote in the tradition of the late Sen. Kennedy.

This race is especially critical and has, as such, drawn national attention because it could possibly break Democrats’ 60 seat majority in the Senate. Presently, Democrats hold 60 seats, enough to block Republicans from even filibustering Democratic-backed bills. However, were Scott Brown to win, he would break that hold, giving Republican groups hope and incentive to attempt to win this election.

Voters across the state have likely had a hard time missing a spate of pro-Brown, anti-healthcare reform ads funded by the Our Country Deserves Better Political Action Committee, otherwise known as the Tea Party.

Joe Wierzbicki, press spokesman for Our Country Deserves Better, said his organization has decided to back Brown because of the election’s potential effect on the composition of the Senate.

“We got involved largely because this race has national ramifications,” said Wierzbicki. “If Scott Brown wins, it could bring a halt to the Democrats’ healthcare plan in Congress, which our organization vehemently opposes,” he added.

According to Wierzbicki, the Tea Party will ultimately have placed a great investment in this race, as the PAC will have spent $300,000 supporting Brown by Tuesday.

Despite tight poll numbers, Wierzbicki predicted voters’ dissatisfaction with America’s political status could translate to a Republican victory in Massachusetts.

“Because people are not happy with the way things are going on in America [Brown could win],” he said.

Locally, campus political groups were scrambling to get out the vote and show their support in a race that has ended up tighter than most anticipated.

Derek Khanna, president of the University of Massachusetts Republican Club, said that he and the club as a whole were supporting Scott Brown.

“I’ve been working for the Scott Brown campaign for a couple of months,” said Khanna. “The club chose to support Scott Brown in the fall.”

On the election, Khanna said he feels that since the late Sen. Kennedy is no longer on the ballot, anything is possible.

“I have said for some time that it is possible for a Republican to be elected as senator in Mass. provided that Kerry or Kennedy is not running for re-election,” he said.

A Kennedy who will appear on the ballot as an independent candidate, Joseph Lewis Kennedy, a Libertarian and information technology executive, has no relation to the late Sen. Kennedy.

“Much of Western Mass. is majority Republican,” he elaborated, “and suburbs of Boston as well are Republican.”

Khanna also pointed to voter disenchantment with the status quo as a factor working to Brown’s favor.

“If the polling data shows Coakley slightly ahead and Republicans are energized and Democrats are disenchanted, Brown will win,” he said.

Conversely, UMass Democrats President Charlie Felder said Brown’s attempt to cast himself as an independent was pure politics, and feels Brown is a conservative Republican who would work to block the Obama administration’s agenda.

“The choices in this election could not be clearer,” said Felder. “Scott Brown is barely working to conceal the fact that he is nothing more than a conservative wolf in an outsider sheep’s clothing.”

Felder further held that he believes Brown will work to impede President Obama’s progressive agenda, while he feels Coakley will vote on a similar line to the late Sen. Kennedy.

“[Brown] will do nothing but serve as a roadblock to the progressive Obama agenda that is slowly moving us away from the destructive and failed conservative policies left in place by an incompetent Republican administration,” Felder said. “This is an election to replace the late, great Ted Kennedy; electing Scott Brown to Sen. Kennedy’s seat would not simply stand as a slap in the face to all of the causes for which Kennedy fought his entire life, but would ensure a rapid reversal and abandonment of the values that define us as Massachusetts residents.”

UMass journalism professor Ralph Whitehead, an expert on Massachusetts politics, said that while he has no idea what the outcome of the election will be, he believes it is a vote not only on the personalities of the candidates, but also on the governing of Democrats in Boston and Washington.

“This election is at least three elections,” said Whitehead. “A referendum on the public personalities of the two major party candidates, a referendum on the Democrats on Beacon Hill [and] a referendum on the Democrats in Washington.”

In addition, Whitehead said that the election’s timing in mid-January could make for low turnout.

“Because only one office is on the ballot and because election day is in the middle of the chilly month of January, the number of people who turn out to vote is likely to be smaller than the number who would turn out to vote for a regular election,” he said.

Despite the attention the Brown campaign has received, Whitehead cautioned that it may be too early to make any sweeping statements about the nature of Massachusetts politics changing.

“We don’t yet know for sure if Blue Massachusetts is trending Red,” he said. “If Brown were to win, would it be because some of the people who voted blue in November of 2008 later shifted their outlook and voted red in January of 2010?” he posited, “or would it be because the percentage of voters who are Blue is just as high as it was in November of 2008, but these voters didn’t turn out at a high enough rate to elect Coakley?” Whitehead stated.

Lastly, Whitehead said a hearty Coakley victory would quell the momentum Republicans have accumulated on a national level and would allow the Democrats to set their own agenda.

“If Coakley wins by a healthy margin, all of the national hubbub will die down, and the Democrats in Washington will try to proceed as they have been planning to proceed,” he said.

On the other hand, “if [state] Sen. Brown wins,” Whitehead speculated, “he will become a national political celebrity overnight, the toast of Red America, and his victory will be interpreted by Democrats as well as by Republicans as a protest against the Democrats in Washington.”

Locally, Whitehead predicted high turnout and ardent support for Coakley.

“We should expect the voter turnout to be extremely high, as high as it is for a general election for Congress in a nonresidential year – and for Coakley to get at least 85 percent of the vote,” he said.

Polls will be open in Amherst from 7 a.m. to 8 p.m. Amherst polling places include the North Congregational Church at 1193 North Pleasant St., North Fire Station at 603 East Pleasant St., Immanuel Lutheran Church at 867 North Pleasant St., Bangs Community Center at 70 Boltwood Walk, Fort River School at 70 South East St., Crocker Farm School at 280 West St., Munson Memorial Library on South Amherst Common at 1046 South East St. and Wildwood Elementary School at 71 Strong St.

Sam Butterfield can be reached at [email protected].