Coming out of the woodwork, former President George W. Bush has decided to lend his support to vulnerable incumbents in the 2016 Senate election.

The New York Times reports that in the coming weeks, Bush will be campaigning for Sens. Roy Blunt (R-MO), Ron Johnson (R-WI), and Rob Portman (R-OH). Since Trump became the presumptive Republican presidential nominee, Bush has also participated in fundraisers for Sens. Kelly Ayotte (R-NH) and John McCain (R-AZ).

Bush's decision to participate in the election cycle marks a stark shift from his previous abstention from politics since the end of his second term in 2008. Aside from minor campaigning for his brother Jeb during the Republican primaries, Bush has mostly stayed under the radar — until now.

The likely reason is that until recently his unfavorability among the general public overshadowed the value of his endorsement. Years after leaving office, his approval ratings seem to be on the rise. According to a 2015 CNN poll, 52 percent of Americans had a favorable impression of him, up from 2009 when only around a third of the public approved of him.

So what’s changed? Perhaps whom he’s being compared to. The general unfavorability of presumptive Republican presidential nominee Donald Trump has just hit an all-time high at 70 percent disapproval, according to a new Washington Post/ABC News poll. This has caused Republican senators in tight races to keep him at arm’s length, even retracting previous endorsements.

Trump has proven a problem for some senators up for reelection this year. Ayotte recently said she would "support, but not endorse" Trump.

Johnson, who once associated himself with Trump as "the Ronald and the Donald," now echoes Ayotte’s statement: "To me, support versus endorse are two totally different things," he said. "I intend to support."

Last month, McCain was recorded saying this election may be the "race of his life" due to Trump’s ostracization of Hispanics, who make up a large percentage of Arizona’s electorate.

Just last month, both George W. and George H.W. Bush said they had no plans to endorse Trump as the presidential candidate or attend the party’s convention in Cleveland this summer.

Now the 43rd president hopes to use his influence to maintain the Republican-held Senate as a "check and balance" on the White House. Which potential president he means was not specified.

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