The Fix's Aaron Blake breaks down why Democratic presidential candidate Hillary Clinton chose Sen. Timothy M. Kaine (D-Va.) to be her running mate. (Whitney Leaming/The Washington Post)

Even before Sen. Timothy M. Kaine (D-Va.) was unveiled Friday as Hillary Clinton’s running mate, liberal groups were teed up to criticize the pick.

Kaine’s boosters say that Kaine, a former Virginia governor and chairman of the Democratic National Committee, is far more progressive than many of his critics realize.

But several organizations, including some with ties to Sen. Bernie Sanders (I-Vt.), the runner-up in the Democratic primaries, sharply questioned Kaine’s liberal bona fides, pointing to Kaine’s support of trade deals and regulations favorable to big banks.

Stephanie Taylor, the co-founder of the Progressive Change Campaign Committee, worried that Kaine’s support of a pending trade deal known as the Trans-Pacific Partnership could allow Republican presidential nominee Donald Trump to “outflank” Clinton on trade.

Sen. Timothy M. Kaine of Virginia waves to the crowd before attending a private fundraiser in Rhode Island on Friday. (Bob Breidenbach /Providence Journal via AP)

Trump has been trying to reach out to Sanders supporters and blue-collar Democrats, arguing that his protectionist views are more in line with theirs than those of the presumptive Democratic nominee.

“It’s now more important than ever that Hillary Clinton run an aggressive campaign on core economic ideas like expanding Social Security, debt-free college, Wall Street reform, and yes, stopping the TPP,” Taylor said. “It’s the best way to unite the Democratic Party and stop Republicans from winning over swing voters on bread-and-butter issues.”

On Thursday, as speculation was mounting that Kaine would be Clinton’s choice, Charles Chamberlain, executive director of the activist network Democracy for America, which backed Sanders in the primaries, said that it should be “disqualifying” for any potential Democratic vice-presidential nominee to “help banks dodge consumer protection standards.”

That was based in part on a bipartisan letter that Kaine signed on Monday urging the Consumer Financial Protection Bureau to “carefully tailor its rulemaking” regarding community banks and credit unions so as not to “unduly burden” these institutions with regulations aimed at commercial banks.

On Friday, Norman Solomon, the coordinator of a group billing itself as the Bernie Delegates Network, called Kaine “a loyal servant of oligarchy.”

“If Clinton has reached out to Bernie supporters, it appears that she has done so to stick triangulating thumbs in their eyes,” said Solomon, whose organization claims to represent hundreds of Sanders delegates attending the convention in Philadelphia but is not coordinating with the campaign.

Sen. Timothy M. Kaine (D-Va.) is Democratic presidential candidate Hillary Clinton's running mate. Here's what you need to know about him. (Sarah Parnass,Osman Malik/The Washington Post)

The group has threatened to protest during the Democratic convention with Kaine on the ticket.

Winnie Wong, an Occupy Wall Street veteran who founded the group People for Bernie, was also underwhelmed with Kaine’s pick, calling it “unsurprising and predictable.”

“It shows a woeful disregard to the progressives who fought so hard this year to create conditions for transformational change this country desperately needs,” Wong said. “Team Clinton did the math on this horse race and they are betting on Tim Kaine to court those white male moderate/Indy voters who won’t vote for her. I doubt they can be moved.”

Kaine’s selection was touted by other traditional boosters of the Democratic Party, including several labor union leaders.

Marc Perrone, president of United Food and Commercial Workers International Union, praised Kaine for a long record of having “supported hard-working families and worked to make their lives better.”

“When a plan to sell grocery stores in Virginia was announced earlier this year, threatening the livelihoods of hundreds of UFCW families, Senator Kaine stood with us as we successfully rallied the community to save local jobs.” Perrone said.

Meanwhile, Mary Kay Henry, president of the Service Employees International Union, called Kaine “an experienced leader with a proven track record on issues from raising wages to immigration reform and racial justice.”

In picking Kaine, Clinton passed over two Hispanic candidates who were considered, Julián Castro, the secretary of Housing and Urban Development, and Labor Secretary Thomas E. Perez.

Though many Latino leaders were disappointed, a leading group praised Kaine as “no stranger to the Latino community,” citing the time he spent as a missionary in Honduras.

“He has consistently put emphasis on communicating with our community, hearing and addressing their concerns,” said Pili Tobar, advocacy and communications director for the Latino Victory Project.

The selection of Kaine, meanwhile, received mixed reviews from environmental groups Friday.

The League of Conservation Voters Action Fund proclaimed him an “awesome choice” in a statement.

“As mayor, governor and senator, he has a proven track record as an environmental leader who has worked to combat climate change, grow our clean energy economy and protect special places in Virginia and across the country,” said Tiernan Sittenfeld, the group’s senior vice president of government affairs.

Greenpeace, however, took issue with some of Kaine’s positions on issues related to climate change, with Annie Leonard, the group’s executive director saying “he still has a long way to go” to prove he’s a “progressive force.”

The group praised Kaine’s early opposition to the Keystone XL Pipeline but questioned his stands on fracking and support for natural gas exports.

David Weigel contributed to this report.