Updated

Political attacks on the Koch brothers have emerged as a key, practically everyday part of Senate Majority Leader Harry Reid and his Democratic Party’s 2014 election strategy -- accusing the wealthy conservative donors of trying to buy elections and block aid to Ukraine.

The attacks began in earnest last month when the Nevada Democrat in notable floor speeches accused Charles and David Koch of being “un-American” and “trying to buy America” and continued straight through this week.

“Across the country Republican Senate candidates are embracing a dangerous agenda that’s good for billionaires like the Koch Brothers and bad for nearly everyone else in the country,” the Democratic Senatorial Campaign Committee said Thursday in announcing a record-breaking February fundraising haul of $6.8 million.

That Democrats would attack the Kochs, or mount a counter-attack, is to be expected, considering how their money was instrumental in helping conservative nonprofits assist Republicans in taking the House in the 2010 midterm elections. Furthermore, Reid argues the Kochs are really trying to "buy" elections to advance their self-serving corporate interests of lower taxes and less regulation.

In this cycle, the brothers have already given a reported $30 million to nonprofits such as Americans for Prosperity to help pay for attack ads on ObamaCare and against incumbent Senate Democrats, as they try to defend their party’s six-seat majority in the upper chamber in an increasingly tough political environment.

The group has already spent a reported $700,000 in ads against Arkansas Democratic incumbent Sen. Mark Pryor, who is trailing challenger and Arkansas GOP Rep. Tom Cotton by 3 percentage points, according to an averaging of polls by nonpartisan RealClearPolitics.com

The Koch-backed attacks have also extended into a money war with the pro-Democrat group Senate Majority PAC, which spent a reported $3 million on ads on tough Senate races in Arkansas, Colorado, Louisiana, Michigan and North Carolina and drew a sharp response.

On Friday, Philip Ellender of Koch Industries told Politico the ads marked “the latest round in a series of attacks and attempts to silence private citizens who dare to disagree with the policies of the Majority Leader and the [Obama] administration.”

Ellender also said Reid specifically has decided to focus on “intimidating political opposition and squelching dissent,” instead of creating jobs and improving the lives of Americans.

Republicans, though, are hardly the only ones benefiting from the political spending of well-heeled backers.

Former hedge fund manager and California billionaire Tom Steyer reportedly is planning to spend at least $100 million (half of it his own money) on attack ads this year against candidates who aren’t supporting efforts to address climate change.

And until recently, even some moderate Senate Democrats were enjoying donations from the Koch brothers’ political action committee. But as that money shifted directions, Democrats stopped holding their tongues.

Charles Koch, 78, and David Koch, 73, inherited a small oil company from their father. They expanded worldwide into chemicals, textiles, paper and other products, building a hugely profitable and privately held conglomerate.

Long active in conservative politics, they seized on the 2010 Citizens United court ruling that allows unlimited corporate spending on political campaigns, often without disclosing donors. They helped found Americans for Prosperity, which reported spending $122 million on elections in 2012. In addition, Charles Koch helped start the Washington-based Cato Institute in the late 1970s. The family has given millions to the Libertarian-minded think tank over the years but was involved in a public dispute with leaders several years ago.

As part of the Democratic offensive this year against the brothers, and the apparent attempt to keep criticism about them in the news cycle, Reid and fellow Senate leaders last week suggested the brothers are behind congressional Republicans agreeing to support a Ukraine aid package only in exchange for delays in IRS rules that would impact the political activities of nonprofits like Americans for Prosperity.

Reid returned to the Senate floor last week to say that when Republican senators rush to defend the Koch brothers, they are also defending the brothers’ “radical philosophy.”

He challenged Republicans by asking, “Is even one of you willing to stand up and disavow the Koch brothers’ radical agenda?”

Louisiana Republican Sen. David Vitter has publicly defended the brothers, saying at a recent town hall meeting that they are “two of the most patriotic Americans.”

“God bless the Koch brothers," said Vitter, according to YouTube video posted by trackers American Bridge. “They’re fighting for our freedom.”

The Associated Press contributed to this report.