WASHINGTON - Republican presidential candidate Mitt Romney has surged into a dead heat with Rick Santorum in the Ohio primary, setting up a cliffhanger race on Tuesday, according to a Reuters/Ipsos poll released on Sunday.

The former Massachusetts governor and former U.S. senator from Pennsylvania are tied with 32 percent support from likely voters in the Ohio Republican primary, the most important of the 10 state nominating contests on "Super Tuesday" this week.

After his victory in Saturday's Washington state caucuses, Romney is gaining momentum going into Tuesday after trailing Santorum in recent polls in Ohio.

"This race could really go either way between now and Tuesday," said Ipsos pollster Chris Jackson.

"If Mitt Romney is able to close this out and win this race, that gives him a leg up in going all the way to the convention and winning the Republican nomination."

Romney's easy victory in Washington marked his fourth victory last week after prevailing in Michigan, Arizona and Wyoming.

Ohio is a traditional bellwether state that could play a key role in deciding which Republican candidate challenges President Barack Obama in November's general election.

The poll showed Newt Gingrich, the former speaker of the U.S. House of Representatives, with 17 percent support, and Ron Paul, the congressman from Texas, with 6 percent support.

Asked whom they would back in a two-man race, 44 percent of respondents in the online survey said they would support Romney, while 43 percent said they would support Santorum.

Head vs. heart

The poll showed voters were responding to the two candidates for different reasons.

Among those who went with Romney, 44 percent said they backed him because they believed he had a better chance at beating Obama in November, and 37 percent said their main reason for choosing him was his ability to improve the still-tepid economy.

Santorum, a strict conservative on social issues such as abortion and gay rights, attracted voters who were interested in his principles. Of the respondents who supported him, 56 percent said they did so because he shared their values and beliefs.

"We sort of see that split in the Republican Party between people who are looking for a candidate that believes the same things they do versus the candidate who will perform the best" nationally, said Jackson, comparing the difference to a decision between the "head" and the "heart."

"The most interesting thing that's going to come out of Ohio is seeing which way the Republican (party) goes as a group."

Romney, a multi-millionaire and former private equity executive, has played up his business experience as he stumped in Ohio, where unemployment is falling but still high.

"We need a president who knows the economy to fix the economy," he said on Saturday at an event in Beavercreek.

Other important states with contests on Tuesday include Georgia, Tennessee and Idaho.

The Ohio poll, conducted between March 1-3 , included a sample of 917 likely voters in the Republican primary election.

Statistical margins of error are not applicable to online surveys, but this poll has a credibility interval of plus or minus 3.8 percentage points for registered voters.