Ron Paul vowed today he'll stay in the GOP race through the national convention in Tampa and defended his decision to campaign in Maine while his rivals are focused on Florida.

"We're going to stay in and see what comes of it," the Texas congressman said on CNN's State of the Union program, in response to a question of whether he'd drop his campaign after all the primaries end in June.

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Paul also bemoaned the "rough road" of competing against "establishment money, the big money." The Texas congressman is a prolific fundraiser but usually raises campaign cash in small dollar amounts.

The Florida primary is Tuesday and is the biggest prize to date in the Republican presidential race with 50 delegates. Mitt Romney has expanded his lead over Newt Gingrich by 15 points in a poll released Sunday by NBC News and the Marist Institute.

Paul campaigned Friday and Saturday in Maine, where GOP caucuses are being held Feb. 4-11. The results of a straw poll will be announced Feb. 11.

Paul said he went to Maine "to get delegates" and was encouraged by "tremendous enthusiasm" and "overflow crowds" at his events. There are a total of 24 delegates available in Maine, including those who are members of the Republican National Committee and selected to represent congressional districts.

A delegate tally from the Associated Press shows Romney leading with 33 delegates, followed by Newt Gingrich with 25 and Rick Santorum with 14. The AP tally includes the votes of RNC members who are not bound by the outcome of primaries or caucuses in their states.