BO, only young and healthy folks can get health insurance and once you are out on your own with this 5K benefit you will be taxed! The average policy costs 12K so that is a loss for you.
To use BO's numbers here's how McCain's plan would work:
Your work no longer gets the tax break so they give you the $12K they were spending as increased take home pay. As an employee you're eligible to buy into their insurance pool. You pay the same $12K to the insurance company. However your taxable income has grown and you owe more taxes. At a middle class marginal tax rate of 25% you owe $3K. McCain gives a $5K tax credit. You are AHEAD $2k under McCain with the same health plan!
-$12K work insurance benefit
+$12K take home pay to buy same insurance
-$3K personal taxes @25% marginal rate
+$5K personal tax credit
$2K net gain on your personal tax burden