Several polls have now found lower support for confirming Brett Kavanaugh to the Supreme Court than there was for confirming previous nominees. He is polling a bit worse than Neil Gorsuch did initially, for example.
Pew has a small 41-36 percent plurality for confirmation now, compared to a 44-32 percent split on Gorsuch.
The Morning Consult/Politico poll has a bigger margin, but shows a similar amount of slippage compared to the last nominee. It finds a 40-28 percent split in favor Kavanaugh and had a 43-25 percent plurality for Kavanaugh.
In both cases, the key change seems to be stronger opposition among Democratic voters. In Pew, a 27-point margin against confirming Gorsuch among these voters has become a 47-point margin against Kavanaugh. The Morning Consult/Politico poll found Democrats opposed to Gorsuch by a margin of 21 points and opposed to Kavanaugh by a margin of 33 points.