Lewis is right. Economic assistance such as selling oil and gas supplies to Ukraine are valid and effective measures to take against Putin's empire-building -- or in his case, "rebuilding" -- aspirations. That and the few simple and relatively inexpensive military "saber rattling" efforts I've detailed a couple, if not more, times. Despite the consequences to the budget and the debt, the long-term costs of allowing Putin to reconstruct the Soviet Union is well worth the cost and effort those actions would require.
This stance is far from what a few on here would suggest is "imperialism" or "nationalistic fervor" on my part, or even "neocon self-servism." These actions as detailed by myself thus far in this thread are actions that represent the only rational response to an effort to rebuild the totalitarian regime upon which Putin was diapered, fed and brought to maturity. He is one of the old-line communists who refuses to accept the utter failure of the Soviet system, and whose nationalism demands that he rebuild that system despite that failure, as he knows no other way he can make Russia "great" again. He ignores the fact that democracy and free enterprise are the best answers to his scenario. But he doesn't know that system, grew up not trusting that system, so he has chosen the only ways he knows -- the old ones.
In the process, he is planning on enslaving his country and probably a half-dozen others as well in order to overcome the shortcomings of the politics to which he swears allegiance. The United States cannot allow a return to the Cold War, cannot allow Russia, which may or may not have destroyed all those nukes during the disarmament treaties' enforcement, to become the dominant world power under that system. The reason is simple: To succeed, the Soviet system must consume more and more nations and their resources, and as they use up those resources without being able to make themselves self-sustaining due to gross mismanagement and further failure to understand how to overcome those mistakes, they demand more and more domination.
When they dominate the world, or try to, what then?
It cannot be allowed. No matter the cost.