As Special Counsel Robert Mueller's team probes deeper into potential collusion between Trump officials and representatives of the Russian government, investigators are taking a closer look at political contributions made by U.S. citizens with close ties to Russia.

Buried in the campaign finance reports available to the public are some troubling connections between a group of wealthy donors with ties to Russia and their political contributions to President Donald Trump and a number of top Republican leaders. And thanks to changes in campaign finance laws, the political contributions are legal. We have allowed our campaign finance laws to become a strategic threat to our country.

An example is Len Blavatnik, a dual U.S.-U.K. citizen and one of the largest donors to GOP political action committees in the 2015-16 election cycle. Blavatnik's family emigrated to the U.S. in the late '70s from the U.S.S.R. and he returned to Russia when the Soviet Union began to collapse in the late '80s.

Data from the Federal Election Commission show that Blavatnik's campaign contributions dating back to 2009-10 were fairly balanced across party lines and relatively modest for a billionaire. During that season he contributed $53,400. His contributions increased to $135,552 in 2011-12 and to $273,600 in 2013-14, still bipartisan.

In 2015-16, everything changed. Blavatnik's political contributions soared and made a hard right turn as he pumped $6.35 million into GOP political action committees, with millions of dollars going to top Republican leaders including Sens. Mitch McConnell, Marco Rubio and Lindsey Graham.

In 2017, donations continued, with $41,000 going to both Republican and Democrat candidates, along with $1 million to McConnell's Senate Leadership Fund.