Republican Mark Amodei looks likely to coast to victory ahead of Democrat Kate Marshall in a special House election Tuesday, according to a poll out Monday from Public Policy Polling. 

The poll puts Amodei at 50 percent to Marshall's 37 percent. That marks a big gain for the Republican, who held only 43 percent support when likely voters were polled three weeks ago. 

The other big change in the race has been a shift in enthusiasm within the parties, the poll showed. Earlier in the race, 86 percent of Democrats supported Marshall, while 77 percent of Republicans planned to vote for Amodei. The final weeks of the campaign have turned those numbers upside down, with 83 percent of Republicans pulling for Amodei and only 74 percent of Democrats saying they'll support Marshall. 

Amodei and Marshall are vying to replace former Rep. Dean Heller (R-Nev.), who is now serving in the Senate. 

Part of Marshall's decline may be due to successful attempts by Amodei to run against President Obama instead of Marshall directly. His campaign ads and speeches have repeatedly focused on Obama, and only about a third of voters in the district approve of Obama's performance. 

The poll numbers are backed up by the lopsided enthusiasm shown in the final tally of early votes cast. Fifty-three percent of early votes were cast by registered Republicans, compared to 34 percent by Democrats. Although Republicans have a registration advantage in this rural district that includes Reno, Republican voter turnout exceeded even that advantage. 

"Yes, early voting is along the lines of registration," acknowledged Marshall spokesman James Hallinan. "But the only poll that counts is the one on Election Day." 

Hallinan said the campaign made contact with over 200,000 targeted voters during the course of the campaign, and is confident that last-minute get-out-the-vote efforts will yield enough Democratic voters on Tuesday to put them over the edge. 

The poll by the Democratic polling firm was conducted from Sept. 9-11 and included 629 likely voters. It has a margin of error of plus or minus 3.9 percentage points.