One of the nation’s most respected political forecasters has changed its rating for the U.S. Senate race in Ohio.

The Cook Political Report, an independent, nonpartisan newsletter that analyzes elections, recently downgraded incumbent Republican Rob Portman’s chances of re-election to a second term, changing the Ohio race’s ranking from “Leans Republican” to “Toss-up.”

Portman’s opponent in the fall will be Democrat Ted Strickland, who narrowly lost re-election as governor in 2010.

In making the call, the report cites the effect of the presidential election on the race. Democrats have carried the Buckeye State in the last two presidential elections.

Portman’s relative unfamiliarity with voters was also considered, contrasted to the more well-known Strickland, and the prospect of real estate tycoon and reality TV star Donald Trump being the Republican presidential nominee also played into the ranking. Many analysts have predicted Trump, who has low favorability ratings in general election polling, could have a negative effect on downballot races for Republicans.

The Senate race is considered one of the most competitive in the nation.

Portman holds a significant fundraising advantage over Strickland, but polling in the race has given Strickland a slight lead, with the most recent, conducted by Quinnipiac University from Feb. 16-20, having the former governor up 44 to 42 percent. Strickland’s lead was within the poll’s margin of error.

Another political forecasting group, Larry Sabato’s Crystal Ball, has considered the race “Leans Republican” in their rankings. However, they also predict a Trump nomination could hurt Portman’s chances.

In a scenario Sabato calls a “Trumpmare” for Senate Republicans seeking re-election, several races change categories, with Ohio becoming a “toss-up” in their analysis.