Republican presidential nominee Donald Trump swiped at vulnerable GOP Sen. Mark Kirk (Ill.) on Thursday night, saying it’s Kirk’s fault that he’s facing a loss in his reelection fight since he didn’t get on board with the nominee.

Speaking at a town hall event in Sandown, N.H., Trump was asked about the Republican hold-outs who have refused to support him; earlier that day, 30 former GOP lawmakers announced their steadfast opposition to his candidacy.

{mosads}Trump argued that there are very few Republicans on the sidelines and that those who are will suffer for it.

“I guess there’s a gentleman in Illinois who’s not doing very well,” Trump said, referencing Kirk. “He was actually taking out ads against me. I said, are you sure he’s a Republican? Maybe he’s a Democrat. He’s not doing well, but, hey, that’s his problem. He wasn’t for me and that’s for political reasons.”

Kirk has announced he will not support Trump and has actively run against him in deep-blue Illinois.

Kirk’s challenger, Rep. Tammy Duckworth (D-Ill.), leads him in RealClearPolitics average by 7 points, although two polls from September showed a closer race in the 2- to 5-point range.

Kirk and Wisconsin Sen. Ron Johnson (R) are considered the most vulnerable incumbent Republican senators up for reelection. Both are running in traditionally blue states in a presidential year that tends to favor Democrats.

Still, Trump predicted Republicans would maintain their slim majority in the Senate and took credit for a coattails effect he claimed would ensure the GOP maintains power in the upper chamber.

“If you look at what’s going on — the other day I saw very interesting — the announcer said Donald Trump is having a very positive effect on the Republicans,” Trump said. “The Republicans are going to hold. They’re doing terrifically well, far better than anyone thought, and we’re going to win some states that never in a million years people thought we’d do well.”

The GOP is defending 24 seats this cycle, compared to only 10 for Democrats. If Democrats can net four seats and hang on to the presidency, they’ll reclaim a majority in the Senate.