A string of unrelated events is highlighting divisions among Republicans just when they’d like to show a united front and take full advantage of President Barack Obama’s latest political problems.

Tensions between libertarian-leaning and more mainstream Republicans were on vivid display Tuesday as Sens. Rand Paul and John McCain clashed over Apple Inc.’s tax-avoidance strategies. Paul, a tea party favorite and son of a libertarian hero, had feuded earlier with McCain — the party’s 2008 presidential nominee — over the use of unmanned aircraft to kill suspected terrorists.