Obama is taking unprecedented steps to shape his legacy after the November elections

President Barack Obama is trying to leave his mark on the institution that helped launch his career as a national politician: the US Senate.

On Wednesday, Obama and Vice President Joe Biden waded into the Pennsylvania Senate race, endorsing Katie McGinty in one of the more high-profile state primary contests in the country.

"I am proud to endorse Katie McGinty to be Pennsylvania's next United States Senator," Obama said.

"Katie is a true champion for working families," he added, "with a proven record of taking on big challenges and delivering for people."

McGinty, who has held multiple jobs in Pennsylvania state government, is locked in a tough primary fight with Joe Sestak, a former congressman and retired three-star Navy admiral. Braddock Mayor John Fetterman is also in the fray.

She wasted no time capitalizing the on the Obama endorsement. Her team quickly cut an ad featuring Obama heaping praise upon her. A person close to her campaign told Business Insider that the would go into rotation on Pennsylvania television stations beginning on Friday.

And the campaign reportedly plans to invest more than $1 million behind the spot in order to raise her profile before the April 26 primary.

The winner will go on to face incumbent Republican Sen. Pat Toomey in the fall. Republicans, who have 54 Senate seats, will need to win races like this one in order to thwart Democratic hopes of taking back the chamber.

Here's the Obama ad:

The Pennsylvania race is just the latest contest this election cycle that the president has inserted himself into.

In past cycles, the president has largely stayed on the sidelines during tough primary fights that did not feature Democratic incumbents. But this time, Obama has not hesitated to jump into Senate primary contests between two competing Democratic candidates.

Last month, Obama endorsed former Ohio Gov. Ted Strickland is his primary race against an upstart rival. The president and vice president also endorsed Rep. Patrick Murphy in his Senate primary fight in Florida. Murphy is facing off against Rep. Alan Grayson, the outspoken congressman whose provocative statements have repeatedly made headlines and garnered him a cult following.

With little political risk and high favorable ratings among Democrats, part of the president's rationale this time around appears to be the opportunity to take back the Senate. Washington Democrats had previously signaled that they believe Obama's primary picks would be the strongest in the November general election. 

Democratic strategist Holly Shulman told Business Insider that with Donald Trump appearing likely to clinch the Republican presidential nomination, Obama is trying to exploit Trump's unpopularity by making a big push in down-ballot races.

"Every day that Trump inches closer to the GOP nomination, Democrats are inching closer to retaking the majority in the Senate and quite possibly the House. For that to happen getting a head start and securing resources early for down-ballot Democrats will be key," Shulman said in an email.

She continued:

The president and vice president have been very active in working to build the Democratic Party over the last few years (many fundraisers for the DNC e.g.) so the fact that would want to support down-ballot candidates across the country too makes sense.

Though it's unclear whether Obama's nod has a direct impact on any state or local race, the president's high favorable ratings among Democrats certainly complicated races for candidates that he's snubbed.

Sestak - who lost a surprisingly close 2010 election to Toomey after beating party-switching Sen. Arlen Specter in the Democratic primary - actually led McGinty in polls. Sestak has also partially campaigned on his role in enacting Obama's policies.

In a Wednesday statement, Sestak touted his support for the Affordable Care Act and the Iraqi troop drawdown, issues in which he stood with the president.

"I have never asked the president - nor anyone else in a position of power - to have my 6, not even by asking for their endorsement," Sestak said, a military reference for supporting someone. "As a leader, it is only about having the people's 6, and because I have theirs, they will have mine."

For his part, Grayson argued that Murphy's numerous endorsements from Democratic party leaders actually may hurt his establishment-backed opponent. Grayson said his campaign contributions doubled the month after Obama and Biden endorsed Murphy.

Grayson did not criticize Obama specifically but he told Business Insider that the Democratic establishment had "more interest in throwing their weight around" than winning elections. The winner of the Florida race in November will replace outgoing Sen. Marco Rubio.

"My people are deeply annoyed that the party bosses are trying to dictate the outcome of a party primary. And so they respond by redoubling their efforts and making sure that they don't steal this election from us," Grayson said.

"Voters don't like being told who to vote for," he added. "They just don't. In fact, this year they hate it."