As Donald Trump tries to notch his third win in a row in Tuesday’s Nevada caucuses, his two chief challengers for the Republican nomination appear to be more concerned with fighting it out for second place.

Marco Rubio and Ted Cruz have emerged from the Iowa caucuses and New Hampshire and South Carolina primaries as the best positioned to defeat Trump for the nomination. But as early as Saturday night, after Trump bested both freshmen senators by 10 points in the Palmetto State, the two campaigns were already ratcheting up the attacks—not on Trump, but on each other.