Choosing a vice presidential candidate is, obviously, a big part of any presidential campaign, and the entire media, legacy and otherwise, has been speculating non-stop about who former President Donald Trump may choose for that role. 

That person, whoever he or she may be, is going to have their hands full, and reportedly, one of their assignments will be fundraising. That's not surprising; this is something most second bananas do in political campaigns.

Fundraising ability will be a key factor in former President Trump's choice for his running mate, Republican sources tell Axios.

Why it matters: Whoever Trump picks, raising cash will be one of the would-be VP's top assignments for the rest of the campaign.

• Clicking with Trump, and skill on TV, remain essential prerequisites.
• And although the campaign has received waves of donations since Trump was convicted, money is still a priority.

Zoom in: That helps explain why several of the top contenders to be Trump's VP pick — namely North Dakota Gov. Doug Burgum, Sen. Tim Scott (R-S.C.) and  Sen. J.D. Vance (R-Ohio) — have been particularly active on the fundraising circuit lately.

The three names mentioned - Doug Burgum, Tim Scott, and J.D. Vance - are regularly mentioned as likely VP picks for Trump.

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All three have already been active on the fundraising trail.

Driving the news: Last night, Trump attended a Cleveland fundraiser organized by Vance and Ohio nursing home developer Brian Colleran that brought in more than $5.5 million, according to a person familiar with the event. 

• Vance has been lobbying some of the heaviest hitters in Silicon Valley to back Trump and set up a fundraising dinner with tech entrepreneur David Sacks in San Francisco.

On Wednesday, Burgum had a call with a seven-figure Republican donor that was set up by RNC finance chair Meredith O'Rourke. 

• Next Tuesday, Burgum will be doing a Zoom fundraiser with Doug Lebda, CEO of the online loan marketplace LendingTree. That also was organized by the RNC, according to a copy of the invitation. 

Scott also frequently has been asked by Trump's team to make fundraising calls on Trump's behalf, people familiar with the situation told Axios.

• Scott on Wednesday held a policy summit in Washington, D.C., with billionaires including Ken Griffin and Bill Ackman, who supported Trump's rivals in the primaries.

Trump's eventual choice will, of course, have a lot to do besides fundraising. One of the more entertaining jobs will be savaging Joe Biden's understudy, Kamala Harris, in the eventual VP debate, assuming the Democrats haven't found a way to tactfully nudge the master of nonsensical word salads out of the way yet. 

But the big job is this: Whoever Trump nominates, should he win the election - and at this juncture that looks likely indeed - will be the presumptive 2028 Republican nominee.

It's a tad unusual for a candidate running against an incumbent, but it's important to remember that Donald Trump, when he takes office, does so as a lame duck. He has four years to Make America Great Again before the Constitution says he must pass the baton on, and whoever he chooses as his Veep will be that presumptive recipient. That will require a choice not only on loyalty to Trump (which, candidly, is going to be a huge factor) and agreement with Trump's populist principles but also the right attributes to win in 2028 against whoever the Democrats might throw at him or her.

The former President has said repeatedly that he will announce his choice at this summer's Republican National Convention, which is the usual form. Whoever he picks, we can hope they are prepared for what they are getting themselves into.