The so-called supermajority would allow Democrats to prevent Republicans from slowing or stopping legislation. The last time there was a filibuster-proof Senate was more than 30 years ago in 1977, during President Jimmy Carter's administration.
Even if they don't hit 60, today's voting could earn the Democrats enough seats to at least get close, thanks to the surging popularity at the top of their ticket and the suffering reputation of the GOP. Several experts predict the party has a strong likelihood of picking up seven or eight seats among the 11 most hotly-contested Senate races, putting them on the cusp of achieving a powerful voting majority.
ABCNews.com has focused on several other key Senate races where, if the Democrats succeed, the party will take a strong hold of the Senate.
When Republican Sen. Ted Stevens was found guilty last week on seven felony counts of making false statements in connection with taking money and other favors from supporters, it made the race with Democratic challenger Mark Begich even more of a tossup. But political experts say that even with a political scandal, this race could still go either way.
"One thing that happens when a candidate is in a scandal is that people vote for them because they're seen as an underdog," said Zelizer.
"People could try to defend the state -- between [Republican vice presidential nominee Sarah] Palin and Stevens," said Zelizer.
But Zelizer conceded that because the scandal is at its final stages and "guilty is part of the headline," Republicans may be unable to defend.
But that didn't keep Stevens from trying.
On the eve of Election Day the senator appeared in an infomercial on more than a half-dozen Alaska television stations in an attempt to rally last-minute support.
The two-minute ads showed Stevens telling the people of Alaska: "My Future is in God's hands. Alaska's future is in yours."
We'll likely know who the nation's next president will be by Wednesday morning, but the same is not necessarily true for the next senator from Georgia.
The race in Georgia between incumbent Republican Sen. Saxby Chambliss and Democrat Jim Martin looks increasingly likely to drag on past Election Day.
With third-party Libertarian candidate Allen Buckley pulling votes away from both Chambliss and Martin, it's possible that neither the Democrat nor the Republican will achieve the 50 percent of the vote that is required for victory under Georgia law, stretching the race into a Dec. 2 runoff on and possibly leaving Democrats teetering around the 60 Senate seat mark for nearly a month.
While Obama is not expected to capture Georgia's 15 electoral votes, a recent CNN/Time/ORC poll has him trailing McCain by just 5 percentage points, 52-47. An overwhelming number of African-American voters have turned out to vote early in the state, a result of the Democratic nominees' surging popularity.
"This is a Southern area where Obama's success and excitement could at least close the gap," said Zelizer.
The economy has been another huge issue in Georgia, where Chambliss has been criticized for his support of the $700 billion financial bailout plan that Congress approved last month.
Minnesota is another state where a third-party candidate is complicating the issue. Independent Party candidate Dean Barkley isn't making things easy for Republican incumbent Sen. Norm Coleman and comedian-turned-Democratic challenger Al Franken (yes, that Al Franken).