If he or she is supporting NATO expansion, just write a simple thank you note. Once again I urge you to support NATO membership for Poland, Hungary, and the Czech Republic. I will remember your vote on this issue the next time I get a chance to vote. Just keep on writing. If you get tired of writing, you can also call the senators' offices to express your opinion.
Many senators now have e-mail as well.
The more they hear from you the better. Contact fraternal societies, cultural groups, and social clubs, and find out what they have planned to support NATO expansion. If not, find out why. Join up and help them out. Urge them to put aside all differences and work with other organizations.