Democrat Tim Ryan and Republican JD Vance made their closing arguments to Ohioans on Monday as they both vie to succeed the GOP's Rob Portman in the U.S. Senate. 

The Ohio race is one of the most closely watched races in the midterm elections and could decide whether Republicans or Democrats control the Senate for the second half of President Biden's first term. 

JD Vance, a venture capitalist and author of the bestselling book "Hillbilly Elegy," received former President Trump's endorsement during a contentious Republican primary. 

Jd Vance and Trump

JD Vance speaking in Dayton, Ohio, on Monday alongside former President Trump.  (Fox News)

"Tomorrow, ladies and gentlemen, is a referendum on Joe Biden's failed policies and the fact that Tim Ryan is a rubber stamp for the failed Joe Biden agenda for this country and for the state of Ohio," Vance told a crowd in Dayton. 

A SIMPLE GUIDE TO MIDTERM ELECTIONS, HOW THEY AFFECT THE PRESIDENCY, AND MORE

Trump made his own stop in Dayton to give Vance one final push on Monday, calling him a "MAGA all star." 

"JD will fight for Ohio with every bone in his body," Trump said. "JD knows how important it is to have leaders that put America first, put Ohio first." 

Tim Ryan, a 10-term congressman and former Democratic 2020 presidential primary contender, made stops in Akron and Youngstown on Monday. 

"We are at a moment, at a crossroads, where either the extremists are going to continue to assert themselves into the body politic of the United States of America, or we stop them. That’s what tomorrow is all about," Ryan told a crowd in Akron.  

Rep. Tim Ryan

Representative Tim Ryan, a Democrat from Ohio, speaks during a primary election night event in Columbus, Ohio, U.S., on Tuesday, May 3, 2022.  (Matthew Hatcher/Bloomberg via Getty Images)

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A Real Clear Politics average of recent polls gives Vance an 8-point lead over Ryan.