18 U.S. Code § 2381 states that an individual guilty of treason may not hold an elected position.
Several Russian officials have publicly stated that both the Russian government and members of Trump's presidential campaign have been involved in activities to directly influence the direction of the presidential election.
If the Presidential campaign of President-Elect Donald Trump has had direct contact and dealings with a foreign government for the purposes of influencing the election, then this accusations is serious enough to warrant an official investigation.