“Clinton Inc. is going to be the most formidable fundraising operation for the Democrats in the history of the country.”

Couple Has Raised More Than $1 Billion in Two Decades; Republicans Worry of Early Lead in 2016.

Bill and Hillary Clinton helped raise more than $1 billion from U.S. companies and industry donors during two decades on the national stage through campaigns, paid speeches and a network of organizations advancing their political and policy goals, The Wall Street Journal found.

Those deep ties potentially give Mrs. Clinton a financial advantage in the 2016 presidential election, if she runs, and could bring industry donors back to the Democratic Party for the first time since Mr. Clinton left the White House.

Republicans, while capable of raising similar sums, worry the Clintons will take an early lead in the next presidential race, which is expected to total well above the $2 billion spent in 2012.

“Clinton Inc. is going to be the most formidable fundraising operation for the Democrats in the history of the country. Period. Exclamation point,” said Rick Hohlt, a lobbyist and fundraiser for Republican Party presidential candidates. “It sure causes concern.”

The Journal tallied speaking fees and donations to Mr. Clinton’s 1992 and 1996 presidential campaigns; the Democratic National Committee during Mr. Clinton’s eight years in the White House; Mrs. Clinton’s bids for Senate and president; and the family’s nonprofit entity—The Bill, Hillary and Chelsea Clinton Foundation.

The Journal was aided by the Center for Responsive Politics, a nonpartisan group that tracks election contributions. The center provided an industry breakdown of campaign donations.

In total, the Clintons raised between $2 billion and $3 billion from all sources, including individual donors, corporate contributors and foreign governments, the Journal found. Between $1.3 billion and $2 billion came from industry sources.

By comparison, Presidents George H.W. Bush and George W. Bush raised a total of $2.9 billion for their four presidential bids, their presidential foundations, as well as for the Republican National Committee when they were in the White House. Another member of the Bush family—Jeb Bush, the former Florida governor—has said he would decide by year’s end whether to enter the 2016 race. If he runs, he could challenge Mrs. Clinton’s potential dominance of industry donors.

President Barack Obama, by contrast, raised less than half of his campaign funds from such donors. Industry sources gave two Bushes no more than 60% of the money they raised for their political operations and presidential foundations, according to the Journal’s analysis.

Mrs. Clinton’s office didn’t comment on the Journal’s findings.

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