Until now, Ted Cruz is facing primary challenge Stefano de Stefano and Dan McQueen (former Mayor of Corpus Christi) while Katrina Pierson, national spokesperson for the 2016 Donald Trump presidential campaign could also challenge Cruz in 2018.
In 2005, Ted Cruz, who was at that time Texas Solicitor General, supported John Roberts' nomination as Chief Justice of the United States while Roberts voted in favor of upholding Obamacare in 2012. That is something Donald Trump highlighted in 2016 in order to undermine Cruz.
Could Cruz's past support to John Roberts undermine his credibility and hurt him among social conservatives, Tea Party voters and hard core anti-Obamacare voters during the Republican senatorial primary campaign in Texas in 2018?
http://www.cnn.com/2016/02/03/politics/donald-trump-ted-cruz-obamacare/