(CNN) -- Sen. Barack Obama has called Tuesday's Democratic primary in Indiana a potential "tiebreaker" that could end his protracted fight with Sen. Hillary Clinton.
Sen. Hillary Clinton shares a Dairy Queen blizzard with Sen. Evan Bayh of Indiana Sunday.
Polls will open at 6 a.m. ET in the eastern portion of the state and 7 a.m. ET in the western half, which is in the Central Time Zone. The last polls in the state will close at 7 p.m. ET.
Seventy-two delegates will be at stake.
The race in Indiana is tight. The CNN poll of polls for the Indiana race on Monday has Clinton leading Obama 48 percent to 44 percent with 8 percent unsure. The CNN poll of polls conducted last week had both candidates at 47 percent.
The latest CNN poll of polls is an average of three surveys conducted April 30 to May 4 by Suffolk University, Zogby and American Research Group. A sampling error for the poll of polls can not be calculated.
The primary will be a key test of the two Democratic presidential candidates' support among blue collar voters. Watch how the economy is issue No. 1 in Indiana »
Obama's loss to Clinton in the Pennsylvania primary two weeks ago raised questions about his ability to draw the support of working-class voters. Clinton was able to secure a 10-point win in Pennsylvania by capturing the support of white, blue-collar workers.
Since the Pennsylvania primary, Obama has been dogged by charges of elitism and by the controversy surrounding his former pastor, Rev. Jeremiah Wright Jr. Both factors could undermine Obama's support from the white, blue-collar voters that could determine the Indiana contest.
In a fight that could also influence working-class voters, Obama and Clinton have sparred over Clinton's proposal to suspend the federal gas tax during the summer. Watch Clinton make her final pitch to voters »
Clinton says she backs the tax holiday despite the "elite opinion" of economists who have widely called the tax holiday an ineffective method to lower record gas prices. Watch Obama say how he differs from Clinton »
"I'm not going to put my lot in with economists," Clinton told George Stephanopolous on ABC's 'This Week' on Sunday after he asked her to name a single economist supporting her plan. "If we actually did it right, if we had a president who used all the tools of the presidency, we would design it in such a way that it would be implemented effectively."
Obama has rejected the idea of a gas tax holiday, calling it a "classic Washington gimmick" that would save drivers only 30 cents a day, or about $30 by the end of the summer. Watch Obama call for straight talk in politics »
He also said Clinton's embrace of the idea -- which is also backed by the presumptive Republican presidential nominee, Sen. John McCain -- amounted to "pandering."
"I understand how badly people are hurting. If we're serious about helping them, let's provide them some relief, but let's not pretend that we're doing something by suggesting a gas tax holiday that will not be paid for and frankly, it is very unlikely that you'd see President George Bush sign," Obama told CNN Monday.
Despite the state's working class demographics and the fact that Clinton won neighboring Ohio, the senator from Illinois has some factors favoring him in Indiana.
The northwest corner of the state is within the media market for Chicago, Obama's hometown.
And the primary is open, meaning that independents are allowed to vote in the Democratic primary. Independents have tended to support Obama in previous primaries. E-mail to a friend