Kentucky Sen. Mitch McConnell cruised to a convincing primary victory over tea-party-backed challenger Matt Bevin on Tuesday night, a result that surprised no one -- the GOP leader had been ahead steadily for months -- but served a reminder of  a handful of important political rules.

Here are five.

1. Candidates matter. McConnell isn't out of central casting as a candidate, but he knows what he's good at (raising money, working the levers of power) and what he's not (oozing charisma). And, like all successful candidates, McConnell plays to his strengths and effectively diminishes his weaknesses. Bevin, on the other hand, showed all the rawness of a first-time candidate: his message roamed all over the map, he was unprepared for McConnell's negative assault, and he never seemed to generate much enthusiasm -- even among GOP base voters who were ready to vote against McConnell.

2. The best expenditure a campaign can make is in a good opposition researcher(s). The McConnell oppo team, as expected, did an absolute number on Bevin. While his supposedly unknowing attendance at a cock-fighting event -- what?! -- was the piece de resistance, Bevin slogged through any number of bad stories thanks to the (often invisible) touch of McConnell's campaign. Bevin spent so much time playing defense from the various attacks launched by McConnell, he never had a chance to make the case that McConnell wasn't a real conservative.

3. Be prepared. McConnell saw what happened to the likes of Dick Lugar (R-Ind.), a longtime senator who assumed his time spent in the hallowed halls of Washington -- and in the upper echelon of the Senate Foreign Relations Committee -- ensured that voters in his home state would never get rid of him. McConnell had no illusions that his perch as the top Republican in the Senate would insulate him in the eyes of voters. He raised a ton of money, put his A team on the ground and took Bevin extremely seriously from the start.

4. Co-opt the opposition. What was Bevin's path to victory? Make the race turn on the same dynamic that Rand Paul did in 2010 when he crushed establishment favorite Trey Grayson, whom McConnell had endorsed, in the GOP primary.  Outsider vs. insider. Change agent vs. status quo. Except that McConnell secured Rand Paul's endorsement way back in the spring of 2013 and, just in case that wasn't enough, appointed Paul family consigliere Jesse Benton as his campaign manager. Bevin's ability to latch onto the Rand star (or is it Randstar) was gone, destroyed by the ever-savvy McConnell operation.

5. Beating incumbents is very, very hard.  Barring a major mistake (like Lugar not grasping the depth of his problems) or a tiny electorate (like the Utah GOP convention that ousted Bob Bennett in 2010), it's extremely difficult to beat an incumbent in a primary.  That goes double if it's a Senate incumbent. That should be good news for Mississippi Sen. Thad Cochran, who faces off with state Sen. Chris McDaniel in two weeks.