There are two great things about both the VAT and the proposed gas tax.
One, they aren't progressive taxes, so they are directly connected to consumption, which is a vast improvement over raising the same revenue via the income tax system (Unfortunately, with the Federal government's unquenchable thirst for money to fund Democrat vote-buying entitlements, there's no chance of the income tax being supplanted, they'd just be additional taxes, which is the mushc larger downside).
Two, since they aren't progressive taxes, they would both bite the Democrat base at least as heavily as anyone else, alienate them, and arouse all the opposition to undreamed-of levels flushing many of the SOBs out of their seats in Congress.